Anybody with a high side A/C gauge?

[Zero102]

I am trying to diagnose whether the a/c compressor in my rx-7 has died but I only have a low side pressure gauge. Does anybody have a high side pressure gauge with an R12 fitting on it that can spare a few minutes? I am located in NW calgary, but can bring the car anywhere within a reasonable distance to have it checked.

[Maxt]

Post what the low side is doing, and I probably can tell you whats going on...
If you can meet up during day I have gauge manifold sets.

[Zero102]

Thanks for the offer, I do appreciate it :)
I can't meet up during the work day, but around 5:15 or so I would be available. If that's necessary let's arrange something over PM after.

Here is what I have:
Originally the R12 system in my 87 rx-7 had a leak. I found the condenser to have a pin hole so I tracked down a used one and fitted that. After fitting it I had the system charged with red tek. I took some measurements tonight to better describe the problem:

System off, 15*C ambient - 60psi
When I turn the system off the low side line leaving the evaporator falls to 1-3*C within 30 seconds and the pressure on the low side drops to 30-35psi, the compressor does not cycle, it stays on constantly and there are very few bubbles visible in the sight glass.
After the ac runs for 5-10 minutes the low side pressure has risen to 50-55psi and the return line from the evaporator is between 25 and 40*C depending on how long I let it run. Still no visible bubbles but obviously cooling sucks. The compressor still does not cycle off.

At that point I decided to turn the system off.


I thought at first the compressor couldn't develop the necessary pressure, but the more I think about it the more it seems I am heat soaking the condenser. The mechanical fan is in place and working properly, although I don't have the belly pan on it is located behind the fan/rad/condenser assembly and I am not sure it matters for this?

Tomorrow night I am going to try soaking the condenser with a hose to bring its temperature down and see if that makes the system behave better, if so I suspect I need to address the heat soaking problem and that is probably more of an rx7club type of issue, however if it doesn't get any better, am I looking at the compressor as the next possible cause?

I checked the sanden repair manual (its a sanden sd-708) and it says I should block the condenser with cardboard then run the system to see if the compressor can develop a 350psi pressure differential, if it can then the compressor is good.

Also, I checked the oil in the system, although 4 ounces of it is brand new it is a nice light yellow with no visible debris.

[Maxt]

Is the electric assist fan working? And also it sounds like it might have to much gas in it, and the relief is opening up on the compressor.
Was the system evacuated and was the original charge weight divided by 3?

[Zero102]

There is no electric fan on my car and no place to put one. I was under the impression no na's had one, but maybe it is just because mine is a GX?

The system was evacuated before filling and was charged to the correct level (32oz / 3 = ~10oz), or at least it should have been.

The receiver/dryer was replaced and due to a past leak there was ~4oz of oil added to the system to match the best estimate of what was lost.

Is 60psi with the system off at 15*C too high? Red Tek doesn't really say much about system pressures and the other HC R12 replacements have a roughly equal lack of information....

I am considering switching to R152 just so that I can have some actual information instead of marketing propaganda :(

It would be nice if the system was just overcharged... what a simple solution it would be :)

Could this be a bad txv? Do you know the procedure to access one on a FC rx-7? My FSM doesn't have that section...